Integrated circuits (ICs) are formed on semiconductor substrates such as wafers. The formation of the integrated circuits may include numerous processing steps such as deposition of various layers, etching some of the layers, and multiple furnace treatments. The integrated circuits are then separated into individual dies, which are packaged and attached to circuit boards.
During the various processing steps involved in the creation of the integrated circuits, various layers of different materials, such as conductors, dielectrics, and semiconductors, are formed on the surface of the wafer where the integrated circuits are being formed. The manufacturers of the integrated circuits often test the composition of the various layers to ensure that the proper materials are being deposited on the substrates.
Characterization of these layers can be performed using various techniques such as X-ray Photoelectron Spectroscopy (XPS). X-rays are used in XPS as the primary radiation to excite the emission of photoelectrons from the wafer surface. The energy of these electrons are representative of the elemental bonding state in the surface of the wafer, and their intensity can be used for compositional and thickness analysis. The various films used to fabricate a modern semiconductor device can have very narrow tolerances in order to achieve an acceptable yield. Hence, it is desirable to have improvements in metrology used for assessing the effectiveness of semiconductor manufacturing processes.